According to ITU Standard G. 728, encoded voice signals are transmitted in packet-oriented fashion in PCM-oriented, multiplexed data streams. A packet thereby respectively comprises 10 bits (625 .mu.s) or, respectively, one PCM data word (125 .mu.s). For example, four data streams representing compressed encoded voice signals are multiplexed in PCM data words in a multiplexed, serial data stream. This means that 2 bits for the respective packet-oriented data stream are transmitted in each PCM data word according to G. 728, whereby a packet (10 bits) is formed of 5 sub-packets of 2 bits each.
Further, predetermined bit patterns, i.e. synchronization words are inserted into every data stream according to the ITU Recommendation G. 728. The bits of the bit pattern or of the synchronization words are continuously inserted into every n.sup.th packet of the data stream--for example into every 16.sup.th packet or G. 728 data word. When a predetermined bit pattern or synchronization word is formed by m bits, for example 4 bits, then a predetermined bit pattern or synchronization word is transmitted after n.times.m.times.10 (packet length) bits of a packet-oriented data stream; given a word width of 4 bits and a repetition rate of 16 packets (of 10 bits each), a synchronization word is transmitted after 640 bits of the packet-oriented data stream.
In multiplexed data streams, at least one bit is allocated to a data stream in the respective packet. For example, four data streams encoded according to G. 728 are combined to form a multiplexed, PCM-oriented data stream. Respectively 2 bits (sub-packet) of a packet are thereby allocated to the respective PCM-oriented data stream. The individual bits of the synchronization word are thereby transmitted in the first bit, i.e. the "most significant bit".